1. Field of the Invention
The present invention relates to a wide area protection control measurement system and method for performing protection, control and measurement of an electric power system.
2. Description of the Related Art
In order to stably supply electric power in the power transmission and distribution field, it is indispensable to perform protection, control and measurement for an entire electric power system, including a plurality of electric-supply stations and various apparatus and equipment, targeting a wide area electric power system, and various technologies for this have been proposed.
For example, Japanese Patent Application Laid-Open NO. 2001-45645 discloses a wide area protection technology, where the voltage/current of an electric power system is received by each terminal device installed in a transformer station, the received information is transmitted to a central processing unit via a wide area data network, current differential operation is executed by the central processing unit using each current information of the operation target section, and the presence of an accident in the system is determined.
Japanese Patent Application Laid-Open No. 2004-64974 discloses a wide area protection technology where information required to protect each electric-supply station and power transmission line is collected to a common arithmetic operation device, so as to perform overall monitoring of accidents generated in each electric-supply station and power transmission line, and perform overall protection.
In the conventional wide area protection technologies disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 2001-45645 and 2004-64974, a power monitoring terminal installed in each electric-supply station and an applied arithmetic operation device having a protective operation function installed at the control side are directly connected via a communication network. A concrete protective operation, executed by the applied arithmetic operation device at the control side, is an electric current differential operation for a wide area disclosed in Japanese Patent Application Laid-Open No. 2001-45645, and is an arithmetic operation called “overall protective operation” disclosed in Japanese Patent Application Laid-Open No. 2004-64974. In these prior arts, a single protective operation is respectively executed after the working of the wide area protection system is started by the single protection operation function embedded in the applied arithmetic operation device at the control side in advance, when the wide area protection system is constructed.
On the other hand, implementing protection, control and measurement of an electric power system in many aspects is expected by performing diversified applied arithmetic operation, including various protective operation, control operation and measurement operation using electric quantities measured for the electric power system in a wide range. As a concrete applied arithmetic operation to be added to the above-mentioned prior art, in order to implement such protection, control and measurement in many aspects, determination of an accident point when an accident occurs to a power transmission line, using voltage and current information at both ends of the power transmission line, or calculation of a line constant of a power transmission line, and step-out relay operation, are possible.
However, in Japanese Patent Application Laid-Open Nos. 2001-45645 and 2004-64974, only a single protective operation function, that is, a single applied arithmetic operation function, is assumed as the applied arithmetic operation function for protection, control and measurement that is embedded in the applied arithmetic operation device at the control side, as mentioned above, so a reconsideration of the entire wide area protection system is required in order to add new applied operation functions, and construct a wide area protection control measurement system which implements protection, control and measurement of an electric power system in many aspects. Here “reconsideration of the entire wide area protection system” means to reconsider (1) what kind of information is collected, and (2) how the transmission cycle of the electric quantity collection is determined, or the like, for each applied arithmetic operation function, and to change the configuration of the entire wide area protection system according to the reconsideration result, and to construct a wide area protection control measurement system.
The configuration of an entire wide area protection system like this is normally changed by changing the data transmission software of all the power monitoring terminals installed in each electric-supply station, and manufacturing new hardware of the applied arithmetic operation device in which the software, to implement the applied arithmetic operation function to be added, is embedded. This method for changing the data transmission software for all the power monitoring terminals, however, has problems in terms of economics, since cost increases in proportion to the number of power monitoring terminals.
In other words, in a wide area protection control measurement system, normally it is necessary to collect electric quantities by installing as many power monitoring terminals as possible in the entire electric power system, in order to advance the accuracy of the applied arithmetic operation, therefore the number of power monitoring terminals inevitably increases. If applied arithmetic operation functions need be added in this state, enormous modifications, including a change in the software of the transmission control unit, are required for all the power monitoring terminals, and existing applied arithmetic operation functions may require enormous modifications as well, according to the prior arts of Japanese Patent Application Laid-Open Nos. 2001-45645 and 2004-64974. Also when a new power monitoring terminal is installed, modifications to receive data from the new power monitoring terminal are required for the existing applied arithmetic operation device side as well.
As a method for implementing protection, control and measurement of an electric power system in many aspects while avoiding the reconsideration of the entire wide area protection system, it is possible to construct a wide area protection control measurement system by assuming all the applied arithmetic operation functions that can be implemented in an initial state of constructing the wide are protection system, and embedding a configuration to implement all the assumed functions into the system.
If this method is used, however, it is possible to generate a considerable amount of applied arithmetic operation functions which are embedded in the wide area protection control measurement system, but which are not used and wasted. As a result, this is easily expected to cause economic problems, that is, the ratio of the effective applied arithmetic operation functions which are actually used to the entire applied arithmetic operation functions that were embedded is low, while the initial cost when the wide area protection control measurement system is constructed increases remarkably in proportion to the number of electric-supply stations and the number of applied arithmetic operation functions respectively.
Another method for implementing the protection, control and measurement of an electric power system in many aspects while avoiding reconsideration of the entire wide area protection system is installing a configuration for a single applied arithmetic operation function, similar to those disclosed in Japanese Patent Application Laid-Open Nos. 2001-45645 and 2004-64974 for each applied arithmetic operation function to be added, in other words, separately manufacturing and installing each power monitoring terminal to be installed in each electric-supply station, and the applied arithmetic operation device at the control side for performing applied arithmetic operation. However, in this case, an individual hardware is required for each applied arithmetic operation function to be added, which increases cost in proportion to the number of electric-supply stations, causing economic problems.
The above-mentioned problems resulting from the addition of a new applied computer function are problems which are also generated when a existing applied arithmetic operation function is changed, such as the case of changing the algorithm of an applied arithmetic operation function or changing the type of electric quantity to be used for applied arithmetic operation.